Re: XML DOM Binding for Ada 95 - matter of style

[Marin David Condic <nobody@noplace.com>]

Well, if one believes that there is no value in the Object Oriented 
Design methodology, then I suppose there is no gain. :-)

First, the code would reflect the design. Everything in the XML DOM 
description is done with an eye towards an object oriented 
implementation - a base level node from which all the other nodes are 
derived, overriding and extension of operations, etc. You don't have to 
implement it as object oriented code utilizing tagged records, etc. Its 
just the most natural expression of the design.

Second, should there be extensions in the form of adding new node types 
or new operations to the DOM, the Object Oriented approach makes the 
extension less painful than it would be to modify the discriminated 
record implementation. Maybe it never changes, so maybe that's not a 
gain. Do you really think the standards committee is going to disband 
and declare XML & the DOM frozen for all time? Tagged record 
implementation would sure make it easier for someone else to build upon 
it if the need should arise.

IMHO, something like the DOM - an OOD expression of a desired 
functionality - is exactly the reason Ada invented tagged records. To 
implement it with discriminated records (a feature I always found to 
have too many "gotchas!" built into it anyway) seems awkward and clumsy. 
If you don't think using tagged records to implement something like this 
design is appropriate, what are you saving them for? :-)

MDC



Preben Randhol wrote:
> Marin David Condic wrote:
> 
>>BTW: I never really liked the XMLAda approach of using discriminated 
>>records and thought it should have been built in a more Object Oriented 
>>way using tagged records.
> 
> 
> What is the gain?
> 
> I thought one of the problems with Booch was that it was using tagged
> types too much. Does Charles also use this approach?
> 


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Marin David Condic
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